Locks and latch mechanisms have become more sophisticated in the last several years. However, the devices and techniques used by persons wishing to gain illegal or non-permitted access to buildings, apartment houses and the like have also become more sophisticated. There have been several proposals to provide security devices for such locks which in essence prevent the turning of the latch knob from the outside.
Exemplary of these devices are U.S. patents to SHARMA, U.S. Pat. No. 4,152,911, May 8, 1979; COOK, U.S. Pat. No. 4,279,137, Jul. 21, 1981 and RICHARDS, U.S. Pat. No. 4,869,086, Sep. 26, 1989. The Sharma device is pivotally mounted to the door for movement into and out of interference with movement of the latch knob. The Cook device comprises a piece of plastic having a knob encompassing portion and a door handle encompassing portion. When the knob is turned, the device, which would tend to be turned with the knob, is prevented by cooperation between the handle and the handle encompassing portion of the device. The Richards device uses a VELCRO.RTM. type of material as part of its mechanism to secure the latch turning device to the latch knob associated with the door or handle.
Notwithstanding these prior art devices, a simple device which can be secured to the door and which selectively locks with the latch knob, but which can be easily released, is desirable.